Carlsen is quick to exploit the square that was freed by the queen move to c7. White threatens Be7.
21... f6g7  22. c1e3  22... b8c8  23. f3f2  23... d8c7 A natural move to protect the c5-pawn, but this decision is criticized by the machine. In any case, the position already seems very difficult to play as Black, and it's not easy to let the c5-pawn go.